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All‐polymer solar cells (all‐PSCs) offer promising potential for large‐scale manufacturing due to their remarkable mechanical and thermal stability. However, the limited capacity of polymer acceptors for near‐infrared (NIR) photon harvesting has impeded their progress in semi‐transparent (ST) all‐PSCs. Here, the study develops a pair of new NIR polymer acceptors, named PYSeF‐T and PYSe2F‐T, with mono‐/di‐fluorinated end groups capped to the selenide monomer backbone, respectively. Owing to the stronger intermolecular interaction and intramolecular charge transfer effect of the di‐fluorinated end groups with the selenide backbone, PYSe2F‐T exhibits a stronger crystallinity and a more bathochromic absorption to 1000 nm. When blended with the donor, PM6, the PY2SeF‐T‐based all‐PSC demonstrates a higher efficiency of 16.73% with a remarkable short‐circuit current (JSC) of 27.7 mA cm−2, which is the highest JSC for all‐PSCs. Based on these, the ST device based on PM6:PYSe2F‐T demonstrates a superior efficiency of 12.52% with an average visible transmittance of 26.2% and a light utilization efficiency of 3.28%, outperforming the mono‐fluorinated counterpart. The work provides an in‐depth understanding of the above synergistic effects to develop NIR polymer acceptors and establishes a solid foundation for future investigations into large‐area and flexible ST all‐PSCs. [ABSTRACT FROM AUTHOR]

"Y-series" small-molecule acceptors (SMAs) have attracted extensive research interest as they boost the power conversion efficiencies of organic solar cells (OSCs) and research communities have begun to concentrate on the structure–property relationship and further structural optimization of this "A–DA′D–A" type SMA. In this study, we developed a novel Y-series SMA, called Y6–Se–O, by adopting benzoselenadiazole as the central core and alkoxy side chains on the β-position of thiophene moieties. The alkoxy substitution yields obvious effects on frontier orbitals of molecules and thus open-circuit voltage (VOC) of the corresponding devices. The lowest unoccupied molecular orbital (LUMO) level of Y6–Se–O is up-shifted compared to that of Y6–Se, therefore, a higher VOC of 0.94 V was attained. Additionally, when mixed with the donor polymer PM6, the Y6–Se–O-based blend films can maintain optimal morphology with stronger crystallinity and reasonable phase segregation, which leads to efficient charge dissociation, suppressed recombination, and balanced charge transportation. As a result, the PM6:Y6–Se–O-based devices reached a better efficiency of 17.5%. Our study demonstrated that the introduction of alkoxy side chains is an effective approach to tuning the optoelectrical properties of SMAs and facilitates both VOC and efficiencies. [ABSTRACT FROM AUTHOR]